Myspace is defunct as a social media, except for muscians and artists.
Facebook still has a huge market, but a lot of the younger kids dont use it. "Too much crap" and "too many trolls" on FB is what my kid tells me, but she does use it to connect to other stuff.....like games.
I dont really understand Twitter, because I dont use it. But evidently it is really "Cool". And full of spam, which will be it's downfall.........
The newest sensation is "SnapChat". Posting small vids, which the recipients only get to view one time. Kinda like a mini one sided conversation, IMHO.
One thing I do like is Facetime......
I have been an administrator of forums for a very very long time. I do see the trend for forums to be fading and dying. Although I do not see them becoming extinct. As long as you have people who are looking for "real" converstions, you will still have a forum.